System Discovery and Signaling

ABSTRACT

An extensible communication system is described herein. The system includes a first module for receiving a root index value and for generating a constant amplitude zero auto-correlation sequence based on the root value. The system further includes a second module for receiving a seed value and for generating a Pseudo-Noise sequence based on the seed value. The system further includes a third module for modulating the constant amplitude zero auto-correlation sequence by the Pseudo-Noise sequence and for generating a complex sequence. The system further includes a fourth module for translating the complex sequence to a time domain sequence, wherein the fourth module applies a cyclic shift to the time domain sequence to obtain a shifted time domain sequence.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/648,978 filed on Jul. 13, 2017, now pending, which is a continuationof U.S. patent application Ser. No. 15/065,427 filed on Mar. 9, 2016,now U.S. patent Ser. No. 10/079,708, which claims priority from U.S.Provisional Patent Application No. 62/130,365 filed on Mar. 9, 2015, nowexpired, all of which are incorporated by reference herein in theirentirety.

FIELD OF DISCLOSURE

The present disclosure relates to the field of wireless communication,and more particularly, to a mechanism for enabling robust signaldetection and service discovery in broadcast networks.

BACKGROUND

The broadcast spectrum is divided up into different frequencies andallocated among different broadcasters for various uses in differentgeographic regions. The frequencies of the spectrum are allocated basedon licenses granted to the broadcasters. Based on the allocations, abroadcaster may be limited to broadcasting a specific type of content,such a television signal, on a certain frequency within a certaingeographic radius. Broadcasting outside of an allocated spectrum couldbe a violation for the broadcaster.

If a broadcaster wishes to transmit another type of content within thatgeographic radius, the broadcaster may be required to obtain anadditional spectrum license and in turn be allocated an additionalfrequency within that frequency. Similarly, if a broadcaster wishes totransmit content within another geographic radius, the broadcaster maybe required to obtain an additional spectrum license for that region.Obtaining additional spectrum licenses, however, may be difficult, timeconsuming, expensive, and impractical.

In addition, a broadcaster may not always fully utilize an entireportion of spectrum for which it has been granted a license. This maycreate inefficiencies in the utilization of the broadcast spectrum.

Moreover, the anticipated use of the broadcast spectrum may be changing.For example, current broadcast television solutions are monolithic anddesigned for a primary singular service. However, broadcasters mayanticipate providing multiple wireless-based types of content, inaddition to broadcast television in the future, including mobilebroadcasting and IoT services. In particular, there are many scenarioswhere a large number of devices may all wish to receive identical datafrom a common source beyond broadcast television. One such example ismobile communication services, where a large number of mobilecommunication devices in various geographic locations may all need toreceive a common broadcast signal conveying the same content, such as asoftware update or an emergency alert, for example. In such scenarios,it is significantly more efficient to broadcast or multicast the data tosuch devices rather than individually signaling the same data to eachdevice. Thus, a hybrid solution may be desirable.

To more efficiently utilize the broadcast spectrum, different types ofcontent may be time-multiplexed together within a single RF channel.Further, different sets of transmitted content may need to betransmitted with different encoding and transmission parameters, eithersimultaneously, in a time division-multiplexed fashion (TDM), in afrequency division-multiplexed (FDM), layer division-multiplexed (LDM)or a combination. The amount of content to be transmitted may vary withtime and/or frequency.

In addition, content with different quality levels (e.g. high definitionvideo, standard definition video, etc.) may need to be transmitted todifferent groups of devices with different propagation channelcharacteristics and different receiving environments. In otherscenarios, it may be desirable to transmit device-specific data to aparticular device, and the parameters used to encode and transmit thatdata may depend upon the device's location and/or propagation channelconditions.

At the same time, the demand for high-speed wireless data continues toincrease, and it is desirable to make the most efficient use possible ofthe available wireless resources (such as a certain portion of thewireless spectrum) on a potentially time-varying basis.

SUMMARY

An example extensible communication system is described herein. Thesystem includes a first module for receiving a root index value and forgenerating a constant amplitude zero auto-correlation sequence based onthe root value. The system further includes a second module forreceiving a seed value and for generating a Pseudo-Noise sequence basedon the seed value. The system further includes a third module formodulating the constant amplitude zero auto-correlation sequence by thePseudo-Noise sequence and for generating a complex sequence. The systemfurther includes a fourth module for translating the complex sequence toa time domain sequence, wherein the fourth module applies a cyclic shiftto the time domain sequence to obtain a shifted time domain sequence.

An example extensible communication method is described herein. Themethod comprises the step of receiving a root index value and generatinga constant amplitude zero auto-correlation sequence based on the rootvalue. The method further comprises the step of receiving a seed valueand generating a Pseudo-Noise sequence based on the seed value. Themethod further comprises the step of modulating the constant amplitudezero auto-correlation sequence by the Pseudo-Noise sequence andgenerating a complex sequence. The method further comprises the step oftranslating the complex sequence to a time domain sequence and applyinga cyclic shift to the time domain sequence to obtain a shifted timedomain sequence.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings, structures are illustrated that, togetherwith the detailed description provided below, describe exemplaryembodiments of the claimed invention. Like elements are identified withthe same reference numerals. It should be understood that elements shownas a single component may be replaced with multiple components, andelements shown as multiple components may be replaced with a singlecomponent. The drawings are not to scale and the proportion of certainelements may be exaggerated for the purpose of illustration.

FIG. 1 illustrates an example broadcast network.

FIG. 2 illustrates an example system for originating bootstrap symbols.

FIG. 3 illustrates a complex I/Q constellation of ZC+PN.

FIGS. 4A-4B, respectively, illustrate example frame controlcompositions.

FIG. 5 illustrates example field termination signaling.

FIG. 6 illustrates an example signal waveform illustrated in FIG. 1.

FIG. 7 illustrates an example system for originating bootstrap symbols.

FIG. 8 illustrates an example PN sequence generator.

FIG. 9 is an example illustration of the mapping of frequency domainsequence to subcarriers.

FIGS. 10A-10B illustrate example time domain structures.

FIG. 11 illustrates an example for originating bootstrap symbols.

DETAILED DESCRIPTION

Described herein is a robust and extensible signaling framework, and, inparticular, a bootstrap signal designed to enable robust detection andservice discovery, system synchronization, and receiver configuration.The bootstrap provides two primary functions: synchronization and thesignaling to discover the waveform being emitted via low level signalingto start decoding a waveform that follows. It is a robust waveform thatprovides extensibility to evolve over time. In particular, the bootstrapsignal works for current broadcasting system but also allows for supportof new services, including mobile broadcasting and IoT services.

A robust signaling system enables a signal to be discovered in highnoise, low ‘carrier to noise ratio’ (CNR), and high Dopplerenvironments. It should be appreciated that it is possible that only thebootstrap signal may be robust, while the actual waveform followingbootstrap may not be as robust. Having a robust bootstrap signal allowssynchronization by receivers to achieve and maintain a lock to thesignal they are picking up in less than ideal environments. When noiseconditions worsen and the receiver can no longer discern the payloadfrom noise, it may still remain locked to the channel through thebootstrap. When noise conditions improve, the receiver does not need togo through the entire re-acquisition process since it already knowswhere to find the channel.

With an extensible signaling system, many different waveforms can besignaled, one for each of the types of services that is going to betransmitted in the future. Thus, new waveforms that don't exist todaythat may need to be used can also be signaled through the bootstrap.

It should be appreciated that the following acronyms and abbreviationsmay be used herein:

-   -   BSR Baseband Sampling Rate    -   BW Bandwidth    -   CAZAC Constant Amplitude Zero Auto-Correlation    -   DC Direct Current    -   EAS Emergency Alert System    -   FFT Fast Fourier Transform    -   IEEE Institute of Electrical & Electronic Engineers    -   IFFT Inverse Fast Fourier Transform    -   kHz kilohertz    -   LDM Layer Division Multiplexing    -   LFSR Linear Feedback Shift Register    -   MHz Megahertz    -   ms millisecond    -   PN Pseudo-Noise    -   μs microsecond    -   ZC Zadoff-Chu

FIG. 1 illustrates an example broadcast network communication system 100including a plurality of content providers 102A, 102B, and 102C(hereinafter content provider 102) providing a variety of types ofcontent 104A, 104B, and 104C (hereinafter content 104) via a broadcastnetwork 106. It should be appreciated that although three contentproviders 102 are illustrated, system 100 may include any suitablenumber of content providers 102. In addition, content providers 102 maybe providers of any suitable types of content, such as televisionsbroadcast signals, software updates, emergency alerts, and so on. Itshould be further appreciated that the content providers 102 may providecontent 104 via either a wireless or wired connection to a gateway 108.

The content 104 is time-multiplexed, at the gateway 108, into a singleRF channel 110. The broadcast receivers 112A, 112B, and 112C(hereinafter broadcast receiver 112) are configured to identify andreceive the broadcast signals 114 via the RF channel 110. It should beappreciated that although three different types of broadcast receivers112 are illustrated (a laptop computer 112A, a mobile telephone 112B,and a television 112C), system 100 may include any suitable number andtype of broadcast receivers 112.

A bootstrap (not shown) indicates, at a low level, the type or form of asignal 114 that is being transmitted during a particular time period, sothat the broadcast receiver 112 can discover and identify the signal114, which in to indicates how to receive the services that areavailable via that signal 114. Thus, the bootstrap is relied on as anintegral part of every transmit frame to allow for sync/detection andsystem configuration. As will be described, the bootstrap designincludes a flexible signaling approach to convey frame configuration andcontent control information to the broadcast receiver 112. The signaldesign describes the mechanism by which signal parameters are modulatedon the physical medium. The signaling protocol describes the specificencoding used to communicate parameter selections governing the transmitframe configuration. This enables reliable service discovery whileproviding extensibility to accommodate evolving signaling needs from acommon frame structure. Specifically, the design of the bootstrapenables universal signal discovery independent of channel bandwidth.

The bootstrap also enables reliable detection in the presence of avariety of channel impairments such as time dispersion and multipathfading, Doppler shift, and carrier frequency offset. In addition,multiple service contexts are accessible based on mode detection duringsignal discovery enabling broad flexibility in system configuration. Thebootstrap also facilitates extensibility to accommodate ongoingevolution in service capability based on a hierarchical signalingstructure. Thus, new signal types not yet conceived, could be providedby a content provider 102 and identified within a transmitted signal 114through the use of a bootstrap signal. Moreover, reusable bit-fieldsinterpreted based on the detected service mode/type enable bit-efficientsignaling despite the level of extensibility afforded. In one example,the bootstrap is configured to be a robust signal and detectable even atlow signal levels. As a result, individual signaling bits within thebootstrap may be comparatively expensive in terms of physical resourcesthat they occupy for transmission. Thus, the bootstrap may be intendedto signal only the minimum amount of information required for systemdiscovery and for initial decoding of the following signal.

General Bootstrap Overview

Described herein is a bootstrap, independent of an implementationexample to be described later. As will be described further, ATSC 3.0 isone example implementation of the bootstrap capability and sets certainconstraints to general bootstrap capability. An appreciation of thesegeneral concepts in bootstrap construction will help those skilled inart see the wide applicability of this technology in futurecommunications systems of various bandwidths and frequency bands in RFspectrum.

FIG. 2 illustrates an example system 200 for generating a bootstrap. Thebootstrap signal 202 generated by the system 200 consists of (N) OFDMsymbols labeled (0−N). The frequency occupation, or bandwidth, issmaller than the post bootstrap signal 206, or waveform, by design. Thepost bootstrap signal 204 represents service being signaled by bootstrapand consumed by a receiver. The post bootstrap signal 204 can be anywaveform enabling future flexibility and extensibility as will bediscussed.

Described herein is the bootstrap signal. The baseband sampling rate(BSR) is denoted by the following equation:

BSR=Fs=(N+16)×(M) or Time domain: T _(S)=1/F _(S)  Equ (1)

where F_(S) is the Frequency Sampling, N is the Operational Variable toscale over bandwidth chosen, and M is Factor (MHz) to Choose Bandwidth.

The OFDM subcarrier spacing (in Hz) is defined as:

ΔF=F _(S)/FFT_((Size))  Equ (2)

Where the FIT size is some power of 2 (e.g. 1024, 2048, 4096, 8192 . . .).

In one example (ATSC 3.0) design process for the 6 MHz broadcasttelevision bandwidth in USA, the equation, M=0.384 is chosen because ofan existing relationship to LTE (based on WCDMA). Other relationshipsmay be chosen. Thus, in this one example:

F _(S)=(0+16)×(0.384 MHz)=6.144 MHz;

F _(S)=6.144 MHz,FFT_((Size))=2048; and

ΔF=6.144 MHz/2048=3000 Hz  Equ (3)

A Zadoff Chu sequence length N_((ZC)) is then selected (based on a primenumber) to be mapped over a portion of the FFT_((Size)) to support thebandwidth chosen, Thus,

Bandwidth=ΔF×(N _((ZC))+1);  Equ (4)

wherein the N_(ZC) is mapped to center of Fri (1500 sub-carriersincluding DC) and zero padding is used on remaining sub-carriers. In theATSC 3.0 example, N_((ZC))=1499 was chosen. Thus,

Bandwidth=3000 (Hz)×(1499+1)=4.5 MHz

As a result, in the example ATSC 3.0 implementation described, thedesign consumes a 4.5 MHz bandwidth and has ΔF=3000 Hz which will giveadequate Doppler performance (MPH) for broadcast band in mobileenvironment.

It should be appreciated other selections for parameters in the abovegeneral equations could enable wider bandwidths or frequency bands(Doppler), etc. In particular, although the value (N) is specified inATSC 3.0 as 0, the full range of (0-127) is available for N. In theexample illustrated, N is constrained to N=0 to achieve 6 MHz. However,it should be appreciated that, by substituting N=127, a bandwidthgreater than 50 MHz can be supported. This is illustrative of theextensibility of the bootstrap.

Referring again to FIG. 2, the system further includes a Zadoff-Chumodule or sequence generator 206 and a pseudo noise (PN) module orsequence generator 208. A Zadoff-Chu (ZC) sequence, is a complex-valuedmathematical sequence which, when applied to radio signals results in acouple interesting properties one of which is that of constant amplitudesignal. It can be defined as:

ZC Sequence=e ^(−jπq[k(k+1)/N) ^((ZC)) ^(])  Equ (5)

FIG. 3 illustrates the complex I/Q constellation 300 of ZC+PN in whicheach I/Q value resides on the unit circle 302 and is described as aphase around this unit circle 302, wherein the amplitude is constant.

It should be appreciated that another theoretical property of (ZC) isthat different cyclically shifted versions of root sequence can beimposed on a signal and can result in ideal zero autocorrelation. Agenerated Zadoff-Chu sequence that has not been shifted is known as a“Root Sequence.” Referring again to FIG. 2, symbol#0, which is usedprimarily for synchronization and versioning, has not been shifted.However, it should be appreciated that the theoretic zeroautocorrelation by using a (ZC) alone isn't achieved over a large rangeof cyclic shifts.

As a result of this basic design requirement, the need of a large numberof cyclic shifts with theoretic ideal autocorrelation was foreseen,something not natural to (ZC) alone. Then, through simulation andexperiments, it was discovered and developed that by introducing aPseudo-Noise (PN) sequence, in addition to ZC, all cyclic shifts can beenabled to approach near theoretic ideal autocorrelation.

FIG. 4B shows results of simulation of just a ZC alone and resultingnon-ideal autocorrelation while FIG. 4A is results of simulation of aZC+PN and resulting near ideal autocorrelation is shown. In particular,the PN-sequence phase-rotates individual complex subcarriers retainingthe desirable Constant Amplitude Zero Autocorrelation Waveform (“CAZAC”)properties of the original ZC-sequence, illustrated in FIG. 3. The addedphase rotation is intended to provide greater signal separation betweencyclic shifts of the same root sequence suppressing spuriousauto-correlation responses observed using a ZC-sequence without theaddition of PN-sequence modulation, illustrated in FIG. 4B. Thus, as canbe appreciated, the discovery of (ZC+PN) drastically improves thesignaling robustness and the capacity (number bits per symbol)communicated by mechanism of cyclic shifts.

Referring again to FIG. 2, the first symbol #0 is a Root with no cyclicshift while Symbols 1-N carrying signaling via mechanism of cyclicshifts. Also, it is seen that mapping and zero padding is applied, by amapping module 210, to Symbol #0. The symbols (1-N) have PN added to ZCthat results in reflective symmetry as shown and will be discussed laterby example.

The signal is then sent to an IFFT module 212 and converted fromfrequency domain to the time domain. The signal then is processed intime domain. The signal exiting IFFT is termed “A” which then haspre-fix and post-fix sections derived from “A” known as “B” and “C”. Thesymbol #0 has a time sequence “CAB” while all other symbols have a timesequence of “RCA”. It should be appreciated that the purpose of this isto add robustness and discriminate symbol #0 which is used forsynchronization and versioning.

The length of bootstrap symbols is defined by:

T _(Symbol)=[C±A±B]×T _(S)  Equ (6)

In one example (ATSC 3.0), the symbol length is 500 μs.

To enable capability to extend the number of symbols, a mechanism ofinversion of (ZC) on the last symbol in bootstrap sequence is used, asillustrated in FIG. 5. In particular, field termination is signaled by a180° phase inversion in the final symbol period relative to thepreceding symbol period. Thus, instead of needing to specify in advancehow long a single is going to be in order for the receiver to be able toidentify the end of a signal, the receiver is instead able to look foran inverted symbol in the signal which would indicate the end of thesignal. This allows for the bootstrap to be flexible and extensiblesince advance knowledge of how long a signal is going to be isn'tnecessary. Thus, instead of defining a bootstrap length in advance, andeither wasting extra space or not reserving enough space (in which caseit may not be possible to completely transmit the intended information),the length of the bootstrap is flexible in that it can be discovered.Moreover, an inverted signal may be relatively easy to detect andtherefore not require significant additional resources to implement.

It should be appreciated that the receiver will gracefully ignore aMajor version (Root) that it doesn't understand. This ensuresextensibility without disrupting legacy receivers in future. In fact,one such signaling method is provided by ATSC 3.0 to be discussed laterand is illustrated by Table 2 herein.

FIG. 6 illustrates an example signal waveform 114 illustrated in FIG. 1.The signal waveform 114 includes a bootstrap 602 followed by apost-bootstrap waveform 604 or the remainder of the waveform. Thebootstrap 602 provides a universal entry point into the signal waveform114. It employs a fixed configuration (e.g. sampling rate, signalbandwidth, subcarrier spacing, time domain structure) known to allbroadcast receivers 112.

It should be appreciated that having a flexible or variable samplingdefined in the bootstrap offers flexibility previously unavailable. Inparticular, rather than designing a solution for a specific servicehaving a fixed or defined sampling rate as a function of bandwidth, aflexible sampling rate enable scaling for a variety of differentbandwidths in order to accommodate diverse services with differentrequirements and constraints. Thus, the same system for synchronizationand discovery can be used for a large range of bandwidths and can servea large band, since different sections of a band may be better suitedfor different types of services.

The bootstrap 602 may consist of a number of symbols. For example, thebootstrap 202 may begin with a synchronization symbol 606 positioned atthe start of each waveform to enable service discovery, coarsesynchronization, frequency offset estimation, and initial channelestimation. The remainder 608 of the bootstrap 602 may containsufficient control signaling to permit the reception and decoding of theremainder of the signal waveform 114 to begin.

The bootstrap 602 is configured to exhibit flexibility, scalability, andextensibility. For example, the bootstrap 602 may implement versioningfor increased flexibility. Specifically, bootstrap 602 design may enablea major version number (corresponding to a particular service type ormode) and a minor version (within a particular major version). In oneexample, the versioning may be signaled (as will be described) viaappropriate selection of a Zadoff-Chu root (major version) aPseudo-Noise sequence seed (minor version) used for generating the baseencoding sequence for bootstrap symbol contents. The decoding ofsignaling fields within the bootstrap 602 can be performed with regardto the detected service version, enabling hierarchical signaling whereeach assigned bit-field is reusable and is configured based on theindicated service version. The syntax and semantics of signaling fieldswithin the bootstrap 612 may be specified, for example, within standardsto which the major and minor version refers.

In order to further exhibit scalability and extensibility, the number ofbits signaled per bootstrap 602 symbol can be defined, up to a maximum,for a particular major/minor version. The maximum number of bits persymbol defined by the equation:

(N _(bps)=└log₂(N _(FFT)/CyclicShiftTol)┐)  Equ (7)

where is dependent on the desired cyclic shift tolerance which in turnis dependent on expected channel deployment scenarios and environments.If available, additional new signaling bits can be added to existingsymbols in a backward compatible manner without requiring a change tothe service version.

As a result, the bootstrap 602 signal duration is extensible in wholesymbol periods, with each new symbol carrying up to N_(bps) additionalsignaling bits. Bootstrap 602 signal capacity may thus be dynamicallyincreased until field termination is reached.

FIG. 7 illustrates an example system 700 for originating bootstrap 602symbols. As described, the values used for each bootstrap 602 symboloriginate in the frequency domain with a Zadoff-Chu (ZC) sequence 704modulated by a Pseudo-Noise (PN) cover sequence 702 with a sequencegenerator 708. The ZC-root 704 and PN-seed 702 determine the service'smajor and minor versions, respectively. The resulting complex sequenceis applied per subcarrier at the Inverse Fast Fourier Transform (“IFFT”)input 706. The system 700 further includes a sub-carrier mapping module710 for mapping output of the sequence generator 708 to the IFFT input706. The PN sequence 702 introduces a phase rotation to individualcomplex subcarriers retaining the desirable Constant Amplitude ZeroAuto-Correlation (CAZAC) properties of the original ZC sequence 704. ThePN sequence 702 further suppresses spurious emissions in theautocorrelation response, thereby providing additional signal separationbetween cyclic shifts of the same root sequence.

It should be further appreciated that modulating a ZC sequence with apseudo-noise sequence in particular, gives the waveform differentcharacteristics that makes it easily discoverable. In particular,modulating with a PN sequence results in near ideal correlation withless uncertainty. Such a combination was discovered through simulationafter testing many combinations of algorithms and sequences. Inparticular, modulating a ZC sequence with a PN sequence produced theunexpected result of producing a signal that is easy to correlate towith no spurious signals created during correlation. This leads to asignal which is easily discoverable, meaning a receiver may correlatewith the signal even in high noise settings.

Bootstrap—implementation (ATSC 3.0 Example)

Described herein is an example implementation of the example bootstrap602. It should be appreciated that although the examples describedherein may refer to a specific implementation of as bootstrap, it iscontemplated that the bootstrap 602 will have broader applicationsbeyond the example illustrated below.

Bootstrap Specification—Dimensions

In one example, the bootstrap 602 structure is intended to remain fixedeven as version numbers and/or the other information signaled by thebootstrap 602 evolves. In one example, the bootstrap 602 uses a fixedsampling rate of 6.144 Msamples/second and a fixed bandwidth of 4.5 MHz,regardless of the channel bandwidth used for the remainder of thewaveform 604. The time length of each sample is also fixed by thesampling rate. Thus,

f _(S)=6.144 Ms/sec

T _(S)=1/f _(S)

BW _(Bootstrap)=4.5 MHz  Equ (8)

An FFT size of 2048 results in a subcarrier spacing of 3 kHz.

N _(FFT)=2048

f _(Δ) =f _(S) /N _(FFT)=3 kHz  Equ (9)

In this example, each bootstrap 602 symbol has a time duration of˜333.33 μs. When processed in time domain to be discussed later using(CAB or BCA) the exact length of T_(Symbol) is 500 μs. The overall timeduration of the bootstrap 602 depends on the number of bootstrap 602symbols, which is specified as N. A fixed number of bootstrap 602symbols shall not be assumed.

T _(Symbol)=500 μs  Equ (10)

It should be appreciated that a 4.5 MHz bandwidth may be selected basedon current industry consensus, which also covers 5 MHz as a lowestbandwidth in common use and smaller than 6 MHz broadcast in thisexample. Thus, the baseband sampling rate can be calculated using:

(N+16)×0.384 MHz=6.144 MS/sec. (N=0bootstrap)  Equ (11)

Selecting a 2048 FFT length, which has good gain, results in a Δf of 3KHz which gives good Doppler performance. It should be appreciated thata similar system can be implemented for other sections of the band. Forexample, variation of the same formula, in which the formula and N valuewould be optimized for that specific bandwidth could be used for otherbandwidths such as 20 MHz.

It should be appreciated that basing the BSR formula on a 0.384 MHzfactor, which is related to LTE systems (and a relationship to WCDMA), anew system may be able to work off of oscillator(s) used for otherimplementations. In addition, all 3GPP LTE baseband sampling rates forall current bandwidths described in standards today can also becalculated from the formula by inserting value (N). Thus, adopting theformula allows for future versions of equipment that contain some sortvariation of LTE variation to still work. However, it should beappreciated that the BSR formula may similarly be based on othersuitable factors.

It should be further appreciated that although examples described hereinutilize a selected FFT size of 2048, other suitable FFT sizes maysimilarly be used. A receiver must first synchronize and identify anincoming signal so that it can begin decoding its information. A longersignaling sequence however, such as an FFT size of 2048, has a highergain and is therefore easier to discover since the amount of informationthe receiver has available to find, or correlate to, is larger.

In existing cellular communication, the gain may not be a factor sincecommunication occurs in a unicast nature and primary synchronizationsignal (PSS) is frequently inserted for random access by multiple users.Moreover, broadcasters may not have been concerned about gain in thepast since broadcast may have been generally intended for staticreceivers that were on high grounds. However, when broadcasting tomobile device or to locations with poor reception, higher gain maybecome more important. A mobile device, however, may not have an optimalantenna shape to rely on for gain and may not be ideally positioned forbest reception and therefore mathematical gain may be relied on.

Therefore, longer signal lengths, such as the example FFT=2048, provideslonger sequences to correlate to and therefore results in more robustreception. For example, with a longer signal, the bootstrap may bediscoverable in underground locations, below the noise floor. Inaddition, longer signal lengths also enable more unique sequences. Forexample, each transmitter can be assigned unique sequence and receiverscan then search for sequences independently. This information can beused, by Global Positioning System (GPS) systems for example, tocalculate a position of the receiver using TDOA techniques, is notdiscussed herein.

It should be appreciated that, although other suitable signal lengthsmay be chosen, a signal length of 2048 has been identified herein inorder to optimize performance. In particular, choosing a differentsignal length may result in tradeoffs between different parameters,including the amount of gain which could impact performance.

Bootstrap Specification—Frequency Domain Sequence

In one example, the Zadoff-Chu (ZC) sequence has length N_(ZC)=1499,where this is the largest prime number that results in a channelbandwidth no greater than 4.5 MHz with a subcarrier spacing of f_(Δ)=3kHz. The ZC sequence is parameterized by a root q, which corresponds toa major version number:

$\begin{matrix}{{{z_{q}(k)} = e^{{- j}\; \pi \; q\frac{k{({k + 1})}}{N_{ZC}}}}{where}{q \in \left\{ {1,2,\ldots \mspace{14mu},{N_{ZC} - 1}} \right\}}{and}{{k = 0},1,2,\ldots \mspace{14mu},{N_{ZC} - 1.}}} & {{Equ}\mspace{14mu} (12)}\end{matrix}$

The use of a pseudo-noise sequence to modulate the ZC sequence hasallowed for the relaxation of constrains on the ZC root. While previoussignaling methods that utilized ZC (e.g. LTE Primary SynchronizationSequence) were limited to selecting prime roots to assure goodautocorrelation properties, in this system, the PN modulation allows forgood autocorrelation even when non-prime roots are selected for ZC.Having non-prime roots for ZC allows for the creation of more waveforms,allowing the system to signal more types of services, i.e. creating amore extensible system.

FIG. 8 illustrates an example PN sequence generator 708. The PN sequencegenerator 808 is derived from a Linear Feedback Shift Register (LFSR)802 of length (order) l=16. Its operation is governed by a generatorpolynomial 804 specifying the taps in the LFSR feedback path followed bya mask 806 specifying the elements that contribute to the sequenceoutput 808. Specification of the generator polynomial 804 and initialstate of the registers represents a seed, which corresponds to a minorversion number. That is, a seed is defined as f(g, r_(init)).

The PN sequence generator registers 802 are re-initialized with theinitial state from the seed prior to the generation of the first symbolin a new bootstrap 602. The PN sequence generator 708 continues tosequence from one symbol to the next within a bootstrap 602 and is notre-initialized for successive symbols within the same bootstrap 602.

The output of the PN sequence generator 708 is defined as p(k) whichwill have a value of either 0 or 1. p(0) shall be equal to the PNsequence generator output after the PN sequence generator 708 has beeninitialized with the appropriate seed value and before any clocking ofthe shift register 802. A new output MO shall subsequently be generatedevery time the shift register 802 is clocked on position to the right,Thus, in one example, the generator polynomial 804 for the PN sequencegenerator 708 shall be defined as:

g={g1, . . . ,g0}={1,1,0,0,0,0,0,0,0,0,0,0,0,0,1,1}

where

p(x)=x ¹⁶ +x ¹⁵ +x ¹⁴ +x+1  Equ (13)

FIG. 9 is an example illustration of the mapping 900 of frequency domainsequence to subcarriers. The ZC-sequence value that maps to the DCsubcarrier (i.e. z_(q)((N_(ZC)−1)/2)) is zeroed so that the DCsubcarrier is null. The subcarrier indices are illustrated with thecentral DC subcarrier having index 0.

The product of the ZC and the PN sequences has reflective symmetry aboutthe DC subcarrier. The ZC sequence has a natural reflective symmetryabout the DC subcarrier. A reflective symmetry of the PN sequence aboutthe DC subcarrier is introduced by mirror-reflecting the PN sequencevalues assigned to subcarriers below the DC subcarrier to thesubcarriers above the DC subcarrier. For example, as illustrated the PNsequence values at subcarriers −1 and +1 are identical, as are the PNsequence values at subcarriers −2 and +2. As a result, the product ofthe ZC and PN sequences also has reflective symmetry about the DCsubcarrier.

It should be appreciated that the symmetry described herein enables amore robust signal, making it easier to discover. In particular, thesymmetry acts as an additional aid for discovery (i.e. additional gain).This is an additional feature of the signal that the receiver can lookfor, making it easier to find. Thus, it is one of the elements thatallows the bootstrap to be recognized even below the noise floor.

As the mapping 900 illustrates, the subcarrier values for the n-thsymbol of the bootstrap (0≤n<N_(s)) may be expressed as:

$\begin{matrix}{{s_{n}(k)} = \left\{ \begin{matrix}{{z_{q}\left( {k + N_{H}} \right)} \times {c\left( {{\left( {n + 1} \right) \times N_{H}} + k} \right)}} & {{- N_{H}} \leq k \leq {- 1}} \\{{z_{q}\left( {k + N_{H}} \right)} \times {c\left( {{\left( {n + 1} \right) \times N_{H}} + k} \right)}} & {1 \leq k \leq N_{H}} \\0 & {otherwise}\end{matrix} \right.} & {{Equ}\mspace{14mu} (14)}\end{matrix}$

where

N _(H)=(N _(ZC)−1)/2

and

c(k)=1−2×p(k)

with c(k) having either the value +1 or −1. It should be appreciatedthat the ZC sequence is the same for each symbol, while the PN sequenceadvances with each symbol.

In one example, the final symbol in the bootstrap is indicated by aphase inversion (i.e. a rotation of 180°) of the subcarrier values forthat particular symbol. This bootstrap termination signaling enablesextensibility by allowing the number of symbols in the bootstrap to beincreased for additional signaling capacity in a backwards compatiblemanner without requiring the major or minor version numbers to bechanged. The phase inversion simply involves multiplying each subcarriervalue by e^(jπ)=−1:

$\begin{matrix}{{{\overset{\sim}{s}}_{n}(k)} = \left\{ \begin{matrix}{s_{n}(k)} & {0 \leq n < {N_{s} - 1}} \\{- {s_{n}(k)}} & {n = {N_{s} - 1}}\end{matrix} \right.} & {{Equ}\mspace{14mu} (15)}\end{matrix}$

This phase inversion enables receivers to correctly determine the endpoint of the bootstrap. For example, a receiver may determine theendpoint of a bootstrap for a minor version that is later than the minorversion for which the receiver was designed and that has been extendedby one or more bootstrap symbols. As a result, receivers do not need toassume a fixed number of bootstrap symbols. In addition, receivers mayignore the signaling bit contents of a bootstrap symbol that thereceiver has not been provisioned to decode but still detect thepresence of the bootstrap symbol itself.

Once mapped, the frequency domain sequence is then translated to thetime domain via a N_(FFT)=2048 point IFFT:

$\begin{matrix}{{{\overset{\sim}{A}}_{n}(t)} = {{\sum\limits_{k = {{- {({N_{ZC} - 1})}}/2}}^{- 1}{{{\overset{\sim}{s}}_{n}(k)}e^{j\; 2\; {\pi f\Delta T}_{S}t}}} + {\sum\limits_{k = 1}^{{({N_{ZC} - 1})}/2}{{{\overset{\sim}{s}}_{n}(k)}e^{j\; 2\; {\pi f\Delta T}_{s}t}}}}} & {{Equ}\mspace{14mu} (16)}\end{matrix}$

Bootstrap Specification—Symbol Signaling

information is signaled via the bootstrap symbols through the use ofcyclic shifts in the time domain of the A_(n)(t) time domain sequence.This sequence has a length of N_(FFT)=2048 and thus 2048 distinct cyclicshifts are possible (from 0 to 2047, inclusive). With 2048 possiblecyclic shifts, up to log₂(2048)=11 log₂(2048)=11 bits can be signaled.It should be appreciate that not all of these bits will actually beused. In particular, N_(b) ^(n) represents the number of signaling bitsthat are used for the n-th bootstrap symbol (1≤n<_(S)), and b₀ ^(n), . .. , b_(N) _(b) _(n) ₋₁ ^(n) represent the values of those bits.

The number of active signaling bits in a received bootstrap symbol maybe greater than the number of signaling bits N_(b) ^(n) expected by areceiver. To facilitate future signaling expansion while maintainingbackwards compatibility, a receiver shall not assume that the number ofactive signaling bits in a received bootstrap symbol is no greater thanthe number of signaling bits N_(b) ^(n) expected by that receiver. Forexample, N_(b) ^(n) for one or more specific bootstrap symbols may beincreased when defining a new minor version within the same majorversion in order to make use of previously unused signaling bits whilestill maintaining backward compatibility. Thus, a receiver provisionedto decode the signaling bits for a particular major/minor version mayignore any new additional signaling bits that may be used in a laterminor version within the same major version.

It should be appreciated that, in the examples described herein, thedistance between correlation peaks between a symbol's bootstrap in thetime domain is what encodes signaling information. In particular, thesymbol#0 is the reference point (absolute shift) and the distancebetween that and the subsequent peaks (relative to the first one)carries information. The meaning of that distance can be determined froma defined lookup table, for example. Thus, the receiver is not trying todecode bits but is instead trying to identify correlation peaks. Oncethe receiver finds a peak, it waits for the next one, and the timebetween those holds signaling information. This creates a more robustsystem since time difference between peaks is easier to discover in highnoise conditions, even though using 256 cyclic shifts, for example, torepresent 8 bits of binary information may be relatively expensive.Actual signaling for the payload following the bootstrap, however, maystill include a modulation scheme with actual bits that carryinformation.

In one example, a cyclic shift is represented as {tilde over (M)}_(n)(0≤{tilde over (M)}_(n)<N_(FFT)) for the nth bootstrap symbol(1≤n<N_(S)) relative to the cyclic shift for the previous bootstrapsymbol. {tilde over (M)}_(n) is calculated from the signaling bit valuesfor the n-th bootstrap symbol using a Gray code method. {tilde over(M)}_(n) is represented in binary form as a set of bits m₁₀ ^(n) m₉ ^(n). . . m₁ ^(n) m₀ ^(n). Each bit of {tilde over (M)}_(n) be computed asfollows:

$\begin{matrix}{m_{i}^{n} = \left\{ \begin{matrix}{\left( {\sum\limits_{k = 0}^{10 - i}b_{k}^{n}} \right){mod}\mspace{14mu} 2} & {i > {10 - N_{b}^{n}}} \\1 & {i = {10 - N_{b}^{n}}} \\0 & {i < {10 - N_{b}^{n}}}\end{matrix} \right.} & {{Equ}\mspace{14mu} (17)}\end{matrix}$

where the summation of the signaling bits followed by the modulooperation effectively performs a logical exclusive OR operation on thesignaling bits in question.

This equation ensures that the relative cyclic shift {tilde over(M)}_(n) is calculated to provide the maximum tolerance to any errors atthe receiver when estimating the relative cyclic shift for a receivedbootstrap symbol. If the number of valid signaling bits N_(b) ^(n) for aspecific bootstrap symbol is increased in a future minor version withinthe same major version, the equation also ensures that the relativecyclic shifts for that future minor version bootstrap symbol will becalculated in such a manner that will still allow a receiver provisionedfor an earlier minor version to correctly decode the signaling bitvalues that it is provisioned to decode, and hence backwardcompatibility will be maintained.

It should be appreciated that in general, the expected robustness ofsignaling bit will be greater than that of b_(k) ^(n) if i<k.

In one example, the first bootstrap symbol is used for initial timesynchronization and signals the major and minor version numbers via theZC-root and PN-seed parameters. This symbol does not signal anyadditional information and hence always has a cyclic shift of 0.

The differentially-encoded absolute cyclic shift, M_(n)(0≤M_(n)<N_(FFT)), applied to the nth bootstrap symbol is calculated bysumming the absolute cyclic shift for bootstrap symbol n−1 and therelative cyclic shift for bootstrap symbol n, modulo the length of thetime domain sequence:

$\begin{matrix}{M_{n} = \left\{ \begin{matrix}0 & {n = 0} \\{\left( {M_{n - 1} + {\overset{\sim}{M}}_{n}} \right){mod}\mspace{14mu} N_{FFT}} & {1 \leq n < N_{S}}\end{matrix} \right.} & {{Equ}\mspace{14mu} (18)}\end{matrix}$

The absolute cyclic shift is then applied to obtain the shifted timedomain sequence from the output of the IFFT operation:

A _(n)(t)=Ã _(n)((t+M _(n))mod N _(FFT))  Equ (19)

Bootstrap Specification—Time Domain Structure

Each bootstrap symbol is composed of three parts: A, B, and C, whereeach of these parts consists of a sequence of complex-valued time domainsamples. Part A is derived as the IFFT of the frequency domain structurewith an appropriate cyclic shift applied, while B and C are composed ofsamples taken from A with a frequency shift of +f_(Δ) (equal to thesubcarrier spacing) and a possible phase shift of e^(−jπ) introduced tothe frequency domain sequences axed for calculating the samples of partB. Parts A, B, and C include N_(A)=N_(FFT)=2048, N_(B)=504, andN_(C)=520 samples, respectively. Each bootstrap symbol consequentlycontains N_(A)+N_(B)+N_(C)=3072 samples for an equivalent time length of500 μs.

In one example, a time domain structure includes two variants: CAB andBCA. The initial symbol of the bootstrap (i.e. bootstrap symbol 0),provided for sync detection, employs the C-A-B variant. The remainingbootstrap symbols (i.e. bootstrap symbol n where 1≤n<N_(S)) conforms tothe B-C-A variant up to and including the bootstrap symbol thatindicates field termination.

It should be appreciated that repeating a portion of the bootstrapallows for improved initial synchronization and discovery since thereceiver knows to expect this repetition in a particular order and theremakes the signal easier to discover and lock onto, even in high noiseconditions.

FIG. 10A illustrates an example CAB structure 1010. In this example,part C 1012 is composed of the last N_(B)=504 samples of part A 1014with a frequency shift of +f_(Δ) and a phase shift of e^(−jπ) applied tothe originating frequency domain sequence S_(n)(k) used for calculatingpart A 1014. The samples for part B 1016 can be taken as the negation ofthe last N_(B) samples of a cyclically shifted time domain sequencecalculated, where the input frequency domain sequence is equal toS_(n)(k) shifted one subcarrier position higher in frequency (i.e.S_(n)(k)=S_(n)((k−1+N_(FFT))mod N_(FFT)), with S_(n)(k) being the inputfrequency domain sequence for generating the frequency-and-phase shiftedsamples for part B 1016). Alternatively, the frequency and phase shiftsfor generating the part B 1016 samples can be introduced in the timedomain by multiplying the appropriately extracted samples from part A1014 by e^(j2πf) ^(Δ) ^(t) as shown in equation:

$\begin{matrix}{{S_{CAB}^{n}(t)} = \left\{ \begin{matrix}{A_{n}\left( {t + {1528T_{S}}} \right)} & \left. {0 \leq t < {520T_{S}}} \right) \\{A_{n}\left( {t - {520T_{S}}} \right)} & {{520T_{S}} \leq t < {2568T_{S}}} \\{{A_{n}\left( {t - {1024T_{S}}} \right)}e^{j\; 2\; {\pi f}_{\Delta}t}} & {{2568T_{S}} \leq t < {3072T_{S}}} \\0 & {otherwise}\end{matrix} \right.} & {{Equ}\mspace{14mu} (20)}\end{matrix}$

FIG. 10B illustrates an example BCA structure 1020. In this example,part C 1012 is again composed of the last N_(C)=520 samples of A 1014,but B 1016 is composed of the first N_(B)=504 samples of C 1012 with afrequency shift of −f_(Δ) applied to the originating frequency domainsequences S_(n)(k) used for calculating part A 1014. In a similarfashion to that described with respect to example CAB structure 1010,samples for part B 1016, can be taken as the last N_(B) samples of acyclically shifted time domain sequence calculated, where the inputfrequency domain sequence is equal to S_(n)(k) shifted one subcarrierposition lower in frequency (i.e. S_(n)(k)=S_(n)((k−1) mod N_(FFT)),with S_(n)(k) being the input frequency domain sequence for generatingthe frequency-shifted samples for part B 1016). The frequency shift forgenerating the part B 1016 samples can alternatively be introduced inthe time domain by multiplying the appropriate samples from part A 1014by e−^(j2πf)Δ^(t) with a constant time offset of −520 T, being includedto account for the correct extraction of the appropriate samples part A1014, as illustrated in the equation:

$\begin{matrix}{{S_{BCA}^{n}(t)} = \left\{ \begin{matrix}{{A_{n}\left( {t + {1528T_{S}}} \right)}e^{{- j}\; 2\; {{\pi f}_{\Delta}{({t - 520})}}}} & \left. {0 \leq t < {504T_{S}}} \right) \\{A_{n}\left( {t - {1024T_{S}}} \right)} & {{504T_{S}} \leq t < {1024T_{S}}} \\{A_{n}\left( {t - {1024T_{S}}} \right)} & {{1024T_{S}} \leq t < {3072T_{S}}} \\0 & {otherwise}\end{matrix} \right.} & {{Equ}\mspace{14mu} (21)}\end{matrix}$

It should be appreciated that the samples for part B 1016 may be takenfrom slightly different sections of part A 1014 for each of the CABstructure 1010 and the BCA structure 1020.

Bootstrap Signal Structure

An example bootstrap signal structure is described herein. A signalingset or structure includes configuration parameter values, a list ofcontrol information fields, and an assignment of those values and fieldsto specific signaling bits. It should be appreciated that a bootstrapsignal structure may take other suitable forms, different than theexample described herein.

The example bootstrap signal structure described herein may apply when amajor version number is equal to 0. The corresponding ZC sequence root(q) is 137. The base number of symbols (including the initialsynchronization symbol) in the bootstrap shall be N_(S)=4. It should beappreciated that N_(S)=4 represents the minimum number of symbols thatcan be transmitted. Thus, to enable the transmission of additionalsignaling bits, N_(S)=4 represents the minimum number of symbols (butnot necessarily the maximum) that shall be transmitted within abootstrap signal.

In one example, the generator polynomial for the Pseudo-Noise sequencegenerator is defined as:

g={g ₁ , . . . ,g ₀}={1,1,1,0,0,0,0,0,0,0,0,0,0,0,0,1,1}=[16 15 14 1 0]

p(x)=x ¹⁶ +x ¹⁵ +x ¹⁴ +x+1  Equ (22)

and the initial register state for the Pseudo-Noise sequence generatoris defined as:

r _(init) ={r _(t-1) , . . . ,r ₀}={0,0, . . . ,0,1}  Equ (23)

In one example, the initial register state of the PN sequence generatorfor a selected bootstrap minor version within a given major version isset to a value from a predefined list of values in order to signal thecorresponding minor version that is in use. Table 1 illustrates exampleinitial register states of a PN sequence generator for respective minorversions.

TABLE 1 Initial Register State of PN Sequence Generator r_(init) =(r_(t−1), . . . , r₀) Bootstrap Minor Version Binary Hexadecimal 0 00000001 1001 1101 0x019D 1 0000 0000 1110 1101 0x00ED 2 0000 0001 1110 10000x01E8 3 0000 0000 1110 1000 0x00E8 4 0000 0000 1111 1011 0x00FB 5 00000000 0010 0001 0x0021 6 0000 0000 0101 0100 0x0054 7 0000 0000 1110 11000x00EC

The bootstrap signal structure may include additional signaling fieldsfollowing the major and minor version signals. For example, the signalstructure may include a wake up bit. This can be an emergency alert wakeup bit, for example. This is a 1 bit field that is either on (1) or off(0).

The signal structure may further include a Minimum Time Interval to NextFrame of Same Major and Minor Version field. This is defined as the timeperiod measured from the start of the bootstrap for frame A to theearliest possible occurrence of the start of the bootstrap for frame B.Bootstrap B is guaranteed to lie within the time window beginning at thesignaled minimum time interval value ending at the next-higher minimumtime interval value that could have been signaled. If thehighest-possible minimum time interval value is signaled, then this timewindow is unterminated. An example signal mapping formulas can bedefined as:

$\begin{matrix}{T = \left\{ \begin{matrix}{T = {{50 \times X} + 50}} & \left. {0 \leq X < 8} \right) \\{T = {{100 \times \left( {X - 8} \right)} + 500}} & \left. {8 \leq X < 16} \right) \\{T = {{200 \times \left( {X - 16} \right)} + 1300}} & \left. {16 \leq X < 24} \right) \\{T = {{400 \times \left( {X - 24} \right)} + 2900}} & \left. {24 \leq X < 32} \right)\end{matrix} \right.} & {{Equ}\mspace{14mu} (24)}\end{matrix}$

Thus, an example signaled value of X=10 would indicate that bootstrap Blies somewhere in a time window that begins 700 ins from the start ofbootstrap A and ends 800 ms from the start of bootstrap A.

The quantity is signaled via a sliding scale with increasinggranularities as the signaled minimum time interval value increases. Xrepresents the 5-bit value that is signaled and T represents the minimumtime interval in milliseconds to the next frame that matches the sameversion number as the current frame. Table 2 illustrates example values.

TABLE 2 Example Minimum Time Interval To Next Frame Index Bit ValueMinimum Time Interval (ms) 0 00000 50 1 00001 100 2 00010 150 3 00011200 4 00100 250 5 00101 300 6 00110 350 7 00111 400 8 01000 500 9 01001600 10 01010 700 11 01011 800 12 01100 900 13 01101 1000 14 01110 110015 01111 1200 16 10000 1300 17 10001 1500 18 10010 1700 19 10011 1900 2010100 2100 21 10101 2300 22 10110 2500 23 10111 2700 24 11000 2900 2511001 3300 26 11010 3700 27 11011 4100 28 11100 4500 29 11101 4900 3011110 5300 31 11111 5700

The signal structure may further include a System Bandwidth field. Thisfield signals the system bandwidth used for the post-bootstrap portionof the current frame. Values include 00=6 MHz, 01=7 MHz, 10=8 MHz,11=Greater than 8 MHz. It should be appreciated that the “greater than 8MHz” option facilitates future operation using a system bandwidthgreater than 8 MHz. Receivers that are not provisioned to handle asystem bandwidth greater than 8 MHz could ignore frames where this fieldis equal to 11.

Table 3 illustrates bootstrap signaling fields are mapped to specificsignaling bits and bootstrap symbols, in one example. The mostsignificant to least significant bits of each signaling field are mappedto the specified signaling bits in the given order from left to right.It should be appreciated that b_(i) ^(n) refers to the ith signaling bitof the nth bootstrap symbol, and that bootstrap symbol 0 does not carryany specific signaling bits.

TABLE 3 Example Bootstrap Signaling Bit Mappings # Signaling Bit Mapping(MSB Field Name Bits to LSB) Major System Version Number 0 n/a MinorSystem Version Number 0 n/a Minimum Time Interval to 5 b₃ ¹ b₄ ¹ b₅ ¹ b₆¹ b₇ ¹ Next Frame of Same Major and Minor Version EAS Wake Up 1 b₀ ¹System Bandwidth 2 b₁ ¹ b₂ ¹ BSR_COEFFICIENT 7 b₀ ² b₁ ² b₂ ² b₃ ² b₄ ²b₅ ² b₆ ² Preamble Structure Indicator 6 b₀ ³ b₁ ³ b₂ ³ b₃ ³ b₄ ³ b₅ ³Number of LDM layers 1 b₆ ³

FIG. 11 illustrates an example extensible communication method. At step1102, a first module receives a root index value and generates aconstant amplitude zero auto-correlation sequence based on the rootvalue. At step 1104 a second module receives a seed value and generatesa Pseudo-Noise sequence based on the seed value. At step 1106 a thirdmodule modulates the constant amplitude zero auto-correlation sequenceby the Pseudo-Noise sequence and generates a complex sequence. At step1108 a fourth module translates the complex sequence to a time domainsequence and applies a cyclic shift to the time domain sequence toobtain a shifted time domain sequence.

Any of the various embodiments described herein may be realized in anyof various forms, e.g., as a computer-implemented method, as acomputer-readable memory medium, as a computer system, etc. A system maybe realized by one or more custom-designed hardware devices such asApplication Specific Integrated Circuits (ASICs), by one or moreprogrammable hardware elements such as Field Programmable Gate Arrays(FPGAs), by one or more processors executing stored programinstructions, or by any combination of the foregoing.

In some embodiments, a non-transitory computer-readable memory mediummay be configured so that it stores program instructions and/or data,where the program instructions, if executed by a computer system, causethe computer system to perform a method, e.g., any of the methodembodiments described herein, or, any combination of the methodembodiments described herein, or, any subset of any of the methodembodiments described herein, or, any combination of such subsets.

In some embodiments, a computer system may be configured to include aprocessor (or a set of processors) and a memory medium, where the memorymedium stores program instructions, where the processor is configured toread and execute the program instructions from the memory medium, wherethe program instructions are executable to implement any of the variousmethod embodiments described herein (or, any combination of the methodembodiments described herein, or, any subset of any of the methodembodiments described herein, or, any combination of such subsets). Thecomputer system may be realized in any of various forms. For example,the computer system may be a personal computer (in any of its variousrealizations), a workstation, a computer on a card, anapplication-specific computer in a box, a server computer, a clientcomputer, a hand-held device, a mobile device, a wearable computer, asensing device, a television, a video acquisition device, a computerembedded in a living organism, etc. The computer system may include oneor more display devices. Any of the various computational resultsdisclosed herein may be displayed via a display device or otherwisepresented as output via a user interface device.

To the extent that the term “includes” or “including” is used in thespecification or the claims, it is intended to be inclusive in a mannersimilar to the term “comprising” as that term is interpreted whenemployed as a transitional word in a claim. Furthermore, to the extentthat the term “or” is employed (e.g., A or B) it is intended to mean “Aor B or both.” When the applicants intend to indicate “only A or B butnot both” then the term “only A or B but not both” will be employed.Thus, use of the term “or” herein is the inclusive, and not theexclusive use. See, Bryan A. Garner, A Dictionary of Modern Legal Usage624 (2d. Ed. 1995). Also, to the extent that the terms “in” or “into”are used in the specification or the claims, it is intended toadditionally mean “on” or “onto.” Furthermore, to the extent the term“connect” is used in the specification or claims, it is intended to meannot only “directly connected to,” but also “indirectly connected to”such as connected through another component or components.

While the present application has been illustrated by the description ofembodiments thereof, and while the embodiments have been described inconsiderable detail, it is not the intention of the applicants torestrict or in any way limit the scope of the appended claims to suchdetail. Additional advantages and modifications will readily appear tothose skilled in the art. Therefore, the application, in its broaderaspects, is not limited to the specific details, the representativeapparatus and method, and illustrative examples shown and described.Accordingly, departures may be made from such details without departingfrom the spirit or scope of the applicants general inventive concept.

What is claimed is:
 1. A communication system, comprising: a memoryconfigured to store program instructions; and a processor, uponexecuting the program instructions, configured to: generate aPseudo-Noise (PN) sequence based on a seed value; generate a constantamplitude zero auto-correlation (CAZAC) sequence based on a root indexvalue; map a product of the PN sequence and the CAZAC sequence to aplurality of subcarriers such that each one of the plurality ofsubcarriers has a subcarrier value, wherein: a subcarrier value of a DCsubcarrier of the plurality of subcarriers is zero, and the subcarriervalues of the plurality of subcarriers have reflective symmetry aboutthe DC subcarrier; and translate the subcarrier values of each one ofthe plurality of subcarriers to a time domain sequence, wherein one ormore receiver devices can perform initial synchronization using the timedomain sequence.
 2. The system of claim 1, wherein the time domainsequence is one symbol in a plurality of symbols and the processor; uponexecuting the program instructions, is further configured to: map aproduct of the CAZAC sequence and a second PN sequence to the pluralityof subcarriers across each symbol of the plurality of symbols; whereinthe second PN sequence is a continuously advancing PN sequence acrossthe plurality of symbols.
 3. The system of claim 1, wherein the timedomain sequence is one symbol in a plurality of symbols and theprocessor, upon executing the program instructions, is furtherconfigured to invert the subcarrier values of each one of the pluralityof subcarriers of a final symbol of the plurality of symbols to indicatetermination of the plurality of symbols.
 4. The system of claim 1,wherein the processor, upon executing the program instructions, isfurther configured to apply a cyclic shift to the time domain sequenceto obtain a shifted time domain sequence.
 5. The system of claim 4,wherein the time domain sequence is one symbol in a plurality, ofsymbols and the processor, upon executing the program instructions, isfurther configured to generate the cyclic shift of the one symbol basedon an absolute cyclic shift of a preceding symbol and a relative cyclicshift of the one symbol, the relative cyclic shift being relative to theabsolute cyclic shift of the preceding symbol.
 6. The system of claim 5,wherein the plurality of symbols have a fixed sampling rate and a fixedbandwidth.
 7. The system of claim 6, wherein the fixed sampling rate is6.144 Msamples/second and the fixed bandwidth is 4.5 MHz.
 8. The systemof claim 1, wherein to translate the subcarrier values to the timedomain sequence, the processor, upon executing the program instructions,is configured to translate the subcarrier values to the time domainsequence using a 2048-point inverse Fast Fourier Transform (IFFT).
 9. Amethod, comprising: generating a Pseudo-Noise (PN) sequence based on aseed value; generating a constant amplitude zero auto-correlation(CAZAC) sequence based on a root index value; mapping a product of thePN sequence and the CAZAC sequence to a plurality of subcarriers suchthat each one of the plurality of subcarriers has a subcarrier value,wherein: a subcarrier value of a DC subcarrier of the plurality ofsubcarriers is zero, the subcarrier values of the plurality ofsubcarriers have reflective symmetry about the DC subcarrier; andtranslating the subcarrier values of each one of the plurality ofsubcarriers to a time domain sequence, wherein one or more receiverdevices can perform initial synchronization using the time domainsequence.
 10. The method of claim 9, wherein the time domain sequence isone symbol in a plurality of symbols and the further comprising: mappinga product of the CAZAC sequence and a second PN sequence to theplurality of subcarriers across each symbol of the plurality of symbols,wherein the second RN sequence is a continuously advancing PN sequenceacross the plurality of symbols.
 11. The method of claim 9, wherein thetime domain sequence is one symbol in a plurality of symbols and themethod further comprising: inverting the subcarrier values of each oneof the plurality of subcarriers of a final symbol of the plurality ofsymbols to indicate termination of the plurality of symbols.
 12. Themethod of claim 9, further comprising: applying a cyclic shift to thetime domain sequence to obtain a shifted time domain sequence, whereinthe cyclic shift is representative of communication information; andtransmitting the shifted time domain sequence to the one or morereceiver devices.
 13. The method of claim 12, wherein the time domainsequence is one symbol in a plurality of symbols and the method furthercomprising: generating the cyclic shift of the one symbol based on anabsolute cyclic shift of a preceding symbol and a relative cyclic shiftof the one symbol, the relative cyclic shift being relative to theabsolute cyclic shift of the preceding symbol.
 14. The method of claim13, wherein the plurality of symbols have a fixed sampling rate of 6.144Msamples/second and a fixed bandwidth of 4.5 MHz.
 15. The method ofclaim 9, wherein the translating the subcarrier values to a time domainsequence comprises: translating the subcarrier values to the time domainsequence using a 2048-point inverse Fast Fourier Transform (IFFT).
 16. Atransmitting device, comprising: a memory storing program instructions;and a processor, upon executing the program instructions, configured to:generate a Pseudo-Noise (PN) sequence based on a seed value; generate aconstant amplitude zero auto-correlation (CAZAC) sequence based on aroot index value; map a product of the PN sequence and the CAZACsequence to a plurality of subcarriers such that each one of theplurality of subcarriers has a subcarrier value, wherein: a subcarriervalue of a DC subcarrier of the plurality of subcarriers is zero, andthe subcarrier values of the plurality of subcarriers having reflectivesymmetry about the DC; translate the subcarrier values to a time domainsequence; and transmit the time domain sequence to one or more receiverdevices, wherein the one or more receiver devices can perform initialsynchronization using the time domain sequence.
 17. The system of claim16, wherein the time domain sequence is one symbol in a plurality ofsymbols and the processor, upon executing the program instructions, isfurther configured to invert the subcarrier values of each one of theplurality of subcarriers of a final symbol of the plurality of symbolsto indicate termination of the plurality of symbols.
 18. The system ofclaim 16, wherein the time domain sequence is one symbol n a pluralityof symbols and the processor, upon executing the program instructions,is further configured to: generate a cyclic shift of the one symbolbased on an absolute cyclic shift of a preceding symbol and a relativecyclic shift of the one symbol, the relative cyclic shift being relativeto the absolute cyclic shift of the preceding symbol; and apply thecyclic shift to the time domain sequence to obtain a shifted time domainsequence.
 19. The transmitting device of claim 18, wherein to apply thecyclic shift, the processor, upon executing the program instructions, isfurther configured to: add the relative cyclic shift and the absolutecyclic shift before applying the cyclic shift.
 20. The transmittingdevice of claim 18, wherein the shifted time domain sequence comprisescontrol signaling configured to permit reception and decoding of awaveform.